CREDIT QUALITY ASSESSMENT (information about credit quality indicator by year of origination) (Detail) $ in Thousands	Sep. 30, 2020 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 2,703,250
2019	1,878,403
2018	1,279,725
2017	1,127,260
2016	932,405
Prior	1,415,563
Revolving Loans	997,329
Total	10,333,935
Commercial investor real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	680,857
2019	803,725
2018	485,876
2017	508,924
2016	493,956
Prior	583,951
Revolving Loans	31,413
Total	3,588,702
Commercial investor real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	675,314
2019	799,088
2018	466,850
2017	501,591
2016	493,003
Prior	566,433
Revolving Loans	31,413
Total	3,533,692
Commercial investor real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	5,049
2019	1,617
2018	19,026
2017	232
2016	271
Prior	1,873
Revolving Loans	0
Total	28,068
Commercial investor real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	494
2019	3,020
2018	0
2017	7,101
2016	682
Prior	15,645
Revolving Loans	0
Total	26,942
Commercial investor real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans	0
Total	0
Commercial owner-occupied real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	210,696
2019	397,591
2018	255,235
2017	209,495
2016	209,577
Prior	367,802
Revolving Loans	1,812
Total	1,652,208
Commercial owner-occupied real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	207,879
2019	392,597
2018	248,942
2017	203,649
2016	209,218
Prior	356,393
Revolving Loans	1,812
Total	1,620,490
Commercial owner-occupied real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,324
2019	4,124
2018	5,505
2017	5,381
2016	137
Prior	5,307
Revolving Loans	0
Total	22,778
Commercial owner-occupied real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	493
2019	870
2018	788
2017	465
2016	222
Prior	5,863
Revolving Loans	0
Total	8,701
Commercial owner-occupied real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	239
Revolving Loans	0
Total	239
Commercial AD&C
Financing Receivable, Credit Quality Indicator [Line Items]
2020	359,083
2019	293,857
2018	169,833
2017	76,340
2016	9,554
Prior	2,377
Revolving Loans	83,756
Total	994,800
Commercial AD&C | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	356,246
2019	292,303
2018	169,833
2017	62,582
2016	6,711
Prior	2,377
Revolving Loans	83,756
Total	973,808
Commercial AD&C | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,710
2019	0
2018	0
2017	13,658
2016	0
Prior	0
Revolving Loans	0
Total	15,368
Commercial AD&C | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,127
2019	1,554
2018	0
2017	100
2016	2,843
Prior	0
Revolving Loans	0
Total	5,624
Commercial AD&C | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans	0
Total	0
Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
2020	174,423
2019	84,846
2018	187,470
2017	225,601
2016	169,331
Prior	332,186
Revolving Loans	0
Total	1,173,857
Residential mortgage | 660-850
Financing Receivable, Credit Quality Indicator [Line Items]
2020	169,476
2019	69,350
2018	164,196
2017	207,953
2016	153,302
Prior	285,639
Revolving Loans	0
Total	1,049,916
Residential mortgage | 600-659
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4,235
2019	11,924
2018	12,136
2017	13,559
2016	9,753
Prior	24,752
Revolving Loans	0
Total	76,359
Residential mortgage | 540-599
Financing Receivable, Credit Quality Indicator [Line Items]
2020	321
2019	1,833
2018	5,089
2017	2,722
2016	3,507
Prior	9,270
Revolving Loans	0
Total	22,742
Residential mortgage | less than 540
Financing Receivable, Credit Quality Indicator [Line Items]
2020	391
2019	1,739
2018	6,049
2017	1,367
2016	2,769
Prior	12,525
Revolving Loans	0
Total	24,840
Residential construction
Financing Receivable, Credit Quality Indicator [Line Items]
2020	81,390
2019	67,765
2018	19,900
2017	3,963
2016	2,105
Prior	0
Revolving Loans	0
Total	175,123
Residential construction | 660-850
Financing Receivable, Credit Quality Indicator [Line Items]
2020	79,897
2019	66,861
2018	19,900
2017	3,963
2016	1,736
Prior	0
Revolving Loans	0
Total	172,357
Residential construction | 600-659
Financing Receivable, Credit Quality Indicator [Line Items]
2020	987
2019	904
2018	0
2017	0
2016	369
Prior	0
Revolving Loans	0
Total	2,260
Residential construction | 540-599
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans	0
Total	0
Residential construction | less than 540
Financing Receivable, Credit Quality Indicator [Line Items]
2020	506
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans	0
Total	506
Commercial Business
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,192,841
2019	223,573
2018	154,930
2017	99,042
2016	42,770
Prior	94,920
Revolving Loans	419,170
Total	2,227,246
Commercial Business | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,190,428
2019	215,772
2018	149,231
2017	97,275
2016	37,641
Prior	88,653
Revolving Loans	410,116
Total	2,189,116
Commercial Business | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	249
2019	3,517
2018	1,462
2017	18
2016	1,467
Prior	2,210
Revolving Loans	4,365
Total	13,288
Commercial Business | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,050
2019	3,242
2018	3,287
2017	1,713
2016	2,353
Prior	2,070
Revolving Loans	1,708
Total	16,423
Commercial Business | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2020	114
2019	1,042
2018	950
2017	36
2016	1,309
Prior	1,987
Revolving Loans	2,981
Total	8,419
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3,960
2019	7,046
2018	6,481
2017	3,895
2016	5,112
Prior	34,327
Revolving Loans	461,178
Total	521,999
Consumer | 660-850
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,561
2019	5,345
2018	5,327
2017	2,297
2016	2,772
Prior	23,023
Revolving Loans	420,848
Total	462,173
Consumer | 600-659
Financing Receivable, Credit Quality Indicator [Line Items]
2020	608
2019	747
2018	286
2017	452
2016	1,076
Prior	5,090
Revolving Loans	20,555
Total	28,814
Consumer | 540-599
Financing Receivable, Credit Quality Indicator [Line Items]
2020	49
2019	433
2018	260
2017	93
2016	503
Prior	3,101
Revolving Loans	8,141
Total	12,580
Consumer | less than 540
Financing Receivable, Credit Quality Indicator [Line Items]
2020	742
2019	521
2018	608
2017	1,053
2016	761
Prior	3,113
Revolving Loans	11,634
Total	$ 18,432